Clinical studies related to cardiac pacing have shown that an optimal atrio-ventricular pacing delay (e.g., AV delay or PV delay) and/or an optimal interventricular pacing delay (e.g., VV delay) can improve cardiac performance. However, such optimal delays depend on a variety of factors that may vary over time. Thus, what is “optimal” may vary over time. An optimization of AV/PV pacing delay and/or VV pacing delay may be performed at implantation and sometimes, a re-optimization may be performed during a follow-up consultation. While such optimizations are beneficial, the benefits may not last due to changes in various factors related to device and/or cardiac function.
The following patents and patent applications set forth various systems and methods for allowing a pacemaker, implantable cardioverter-defibrillator (ICD) or other cardiac rhythm management (CRM) device to determine and/or adjust AV/PV/VV pacing delays so as to help maintain the pacing delays at optimal values: U.S. patent application Ser. No. 10/703,070, filed Nov. 5, 2003, entitled “Methods for Ventricular Pacing”; U.S. patent application Ser. No. 10/974,123, filed Oct. 26, 2004; U.S. patent application Ser. No. 10/986,273, filed Nov. 10, 2004; U.S. patent application Ser. No. 10/980,140, filed Nov. 1, 2004; U.S. patent application Ser. No. 11/129,540, filed May 13, 2005; U.S. patent application Ser. No. 11/952,743, filed Dec. 7, 2007. See, also, U.S. patent application Ser. No. 12/328,605, filed Dec. 4, 2008, entitled “Systems and Methods for Controlling Ventricular Pacing in Patients with Long Intra-Atrial Conduction Delays” and U.S. patent application Ser. No. 12/132,563, filed Jun. 3, 2008, entitled “Systems and Methods for determining Intra-Atrial Conduction Delays using Multi-Pole Left Ventricular Pacing/Sensing Leads.” See, further, U.S. Pat. No. 7,248,925, to Bruhns et al., entitled “System and Method for Determining Optimal Atrioventricular Delay based on Intrinsic Conduction Delays.” At least some of the techniques are implemented within the QuickOpt™ systems of St. Jude Medical.
In particular, techniques were set forth within at least some of these patent documents for exploiting various inter-atrial and interventricular conduction delays to determine preferred or optimal AV/PV/VV pacing delays. Techniques were also set forth for exploiting the VV delays to determine which ventricles should be paced—the left ventricle (LV), the right ventricle (RV), both ventricles, or neither, and in which order. In at least some examples, the implanted device (or an external programming device in communication with the implanted device) performs a series of tests to determine intrinsic AV/PV and VV conduction delays from which preferred pacing delays are determined. In particular, an “A sense” test is performed to detect intrinsic intra-atrial delays from which preferred AV/PV pacing delays are determined. A “V sense” test is performed to detect intrinsic ventricular events from which an intrinsic interventricular conduction delay (Δ) is determined. An “RV pace” test and a separate “LV pace” test are performed to detect paced interventricular conduction delays (IVCD_RL and IVCD_LR, respectively) from which an intrinsic interventricular correction term (ε) is determined. The optimal VV delay for use in biventricular pacing is then set based on Δ and ε.
Issues can arise, though, if the patient is subject to an ongoing episode of AF. During AF, the atria of the heart beat chaotically, resulting in irregular AV conduction. As such, it can be difficult to determine values for Δ and ε. For example, due to the irregular AV conduction, the V sense test might not be able to reliably determine the order in time of sensed LV and RV QRS complexes and hence might not be able to reliably determine the value of Δ. (A QRS complex is a portion of an intracardiac electrogram that represents intrinsic ventricular depolarization. Within biventricular systems, separate LV and RV QRS complexes can be detected on respective LV and RV sensing channels.)
Accordingly, some aspects of the invention are directed to providing improved V sense test techniques for use during AF to allow for a reliable determination of Δ despite irregular AF conduction for use in determining optimal VV pacing delays.
Another concern during AF is that the implanted device typically needs to switch to a non-atrial tracking mode (such as VVI, V00, D00) for delivering RV and LV pacing pulses. During a non-atrial tracking mode, it can be difficult to reliably perform the LV pace and RV pace tests to determine values for IVCD_RL and IVCD_LR for use in setting the VV pacing delay. One particular concern is that, during the LV and RV pace tests, QRS complexes can arise in a given ventricular chamber either due to interventricular conduction from the other chamber (triggered by RV or LV pulses) or due to AV conduction from the atria (triggered by atrial P-waves.) An inability to distinguish between these events makes it difficult to reliably determine values for IVCD_RL and IVCD_LR for use in determining ε and setting VV.
Accordingly, other aspects of the invention are directed to providing improved RV pace and LV pace test techniques for use during non-atrial tracking modes to allow for a reliable determination of IVCD_RL and IVCD_LR values for use in determining optimal VV pacing delays.